1. Field of the Invention
The present invention relates to a recording medium on which an image etc. is recorded and which is suitable for use in ink jet recording. More particularly, the present invention relates to a recording medium that maintains the natural characteristics of the base paper, and ensures a high image density, a sharp color tone and a high resolution, while developing good ink absorption.
Further, the present invention relates to a method of producing the recording medium, and an ink jet recording method in which ink is ejected in the form of droplets toward the medium for recording of an image, etc. thereon.
2. Description of the Related Art
Recently, an ink jet recording method has been developed to record an image, characters and so forth by ejecting ink in the form of minute droplets according to any of various operating principles, and depositing the ink droplets on a recording medium made of, e.g., paper. The ink jet recording method has superior advantages such as high-speed operation, low noise, easy realization of multicolor recording, and versatility in recording pattern.
Because of advantageous features requiring neither development nor fixation in addition to the above advantages, the ink jet recording method has become increasingly employed in many applications, including information equipment, for recording various images. Furthermore, an image formed by the multicolor ink jet recording method is comparable in image quality to an image obtained by multicolor printing using a plate-making process and by printing using a color photographic process. In the case of recording an image etc. on a relatively small number of sheets of paper, the recording cost is lower than the cost for producing an ordinary multicolor printing image or a photographic image. For that reason, the ink jet recording method has seen more widespread use even in the field of full-color image recording as well.
In the field of ink jet recording, recording apparatuses and processes have been improved with the advance of recording characteristics such as speedup of recording operation, higher definition, and full-color recording. Correspondingly, improved characteristics have also been demanded for recording media.
The forms of recording media for use in ink jet recording are mainly divided into two types, i.e., the ordinary type represented by fine paper and bond paper, and the coated type manufactured by coating an ink accepting layer on the surface of a support formed of fine paper, synthetic paper, or a synthetic resin film. The coated type is further divided into the low-coated type having a coating weight in the range of about 1 to 10 g/m2, the medium-coated type having a coating weight in the range of about 10 to 20 g/m2, and the high-coated type having a coating weight not less than 20 g/m2.
In the recording media for use in ink jet recording of the medium- or high-coated type using a paper-made support, because sufficient ink absorption is provided by an ink accepting layer formed as a relatively thick coating, ink diffusion (blur) in the two-dimensional directions along the surface of a recording medium is suppressed, and a high-definition, sharp image can be formed by ink jet recording. On the other hand, those recording media have the disadvantages that the natural characteristics of the base paper are lost by the presence of a relatively thick ink accepting layer (the medium-coated type having a thickness of about 10 to 20 xcexcm), and that the recording media cannot be easily handled because of the increase in its thickness and hence in its hardness. For those reasons, recording media of the low-coated type, which do not lose the natural characteristics of the base paper and ease in handling, have been used more favorably in recent years.
For recording media of the low-coated type, however, since all of the ink ejected toward the recording medium cannot be absorbed only by an ink accepting layer, a part of the ejected ink must be absorbed by the base paper. Accordingly, the recording medium of the low-coated type has been produced by employing a base paper having a small Stxc3x6kigt sizing degree and good ink absorption, and coating a thin ink accepting layer over the entire surface of the base paper.
The thus-produced recording medium of the low-coated type is less susceptible to such failures as ink flooding due to insufficient ink absorption and the so-called beading problem in which ink coheres on the surface of the medium to cause unevenness in density. On the other hand, there arise problems that ink diffuses deep into the base paper and an image recorded or printed on the recording medium becomes lighter. Furthermore, in the case of full-color printing wherein a large amount of ink is concentrated in a particular area, the thin ink accepting layer cannot sufficiently hold the ink therein. As a result, the surplus ink diffuses unevenly within the ink accepting layer formed over the entire surface of the base paper in the two-dimensional directions. This uneven diffusion of ink results in the occurrence of whisker-like smears (so-called feathering) extending radially outward from printed dots, and noticeably lowers the printing quality.
Japanese Patent Laid-Open No. 6-312572 discloses a method of trying to suppress diffusion of ink in the two-dimensional directions along the paper surface by coating a thin ink accepting layer, which has a grain size less than {fraction (1/100)} of the size of pulp fibers making up the base paper, so as to completely cover the pulp fibers exposed to the surface of the base paper.
The disclosed method is effective when the amount of ink to be absorbed into the base paper is relatively small. In the case of absorbing a large amount of ink into the base paper, however, it is difficult to suppress diffusion of the ink in the two-dimensional directions along the paper surface.
Japanese Patent Laid-Open No. 11-011014 proposes a method of scattering a hydrophobic material in an ink accepting layer.
With this related art, however, the ink accepting layer must be formed in a relatively thick thickness on the surface of the base paper. Accordingly, the proposed method cannot ensure the retention of the natural characteristics of the base paper and ease in handling as intended by the present invention.
With the view of solving the problems set forth above, an object of the present invention is to provide a recording medium that maintains the natural characteristics of the base paper, and ensures a high image density, a sharp color tone and a high resolution by suppressing diffusion of ink in the two-dimensional directions along the paper surface, while developing good ink absorption.
To achieve the above object, according to the present invention, in a recording medium having an ink accepting layer formed on at least one surface of a base paper, the ink accepting layer is formed in the form of islands scattered on the surface of the base paper.